Coupling for two-pole circuit breaker



April v7, 1970 G. w. KNEQHT" f" rsliz l l COUPLING FOR TWo-PoLE CIRCUITBREAK-ER 2 Sheets-Sheet 1 Fleduune 22. 19e? FILS( 2b INVENTOR.

ATTO NEYS' l April?, 1970 G.Iw. KNr-:CHT I 3,505,621 v COUPLING FonTwo-POLE CIRCUIT BREAKER Filed June 22. 196'?- 2 sheets-sheet 2 mvENToR.650265 nz KA/EcHr A TTORNE YS United States Patent O 3,505,621 COUPLINGFOR TWO-POLE CIRCUIT BREAKER George W. Knecht, Brooklyn, N.Y., assignorto Murray Manufacturing Corporation Filed June 22, 1967, Ser. No.648,123 Int. Cl. H01h 75/10, 77/06 U.S. Cl. 335--8 3 Claims ABSTRACT OFTHE DISCLOSURE A two-pole circuit breaker of the type including twosingle pole breakers of half-inch -module design mounted side-by-sideand interlocked for two pole operation. The interlocking member isshaped in the form of a cylinder having a central flange, the endcylindrical portions are caused, by means of scissor camming action upontheir periphery, to transfer the tripping of one circuit breaker to theother.

BACKGROUND OF THE INVENTION Circuit breakers provide means forprotecting electrical equipment against short and overload conditions,as well as provide a means for controlling the operational status ofassociated equipment via a manually operable switch. The protectionprovided by the circuit breaker is automatic; the breaker responding toa predetermined current condition to open the contacts maintaining theline-to-load continuity. Breakers are classified by the manner in whichthey respond to current. Those which are responsive to the heat effectof current are known as thermal breakers; tho-se which respond to amagnetic flux produced by the current are called electromagneticbreakers, and those which are responsive to both of the foregoing aredesignated thermal magnetic breakers.

The idea of combining two or more breakers, each of which controls asingle line-to-load continuity, for multipole operation is not new. Theart has long recognized that it is very often desirable to cause onecircuit breaker to trip another upon an overload condition occurring inanother breaker.

The requirements for this dependency of the tripping of the breakers,however, often involve diametrically opposed considerations. Forexample, fully magnetic breakers exhibit extremely small tripping forceswhensubjected to overload conditions; consequently, the additional forceloading for tripping the second breaker is a serious problern. Thedesirability of maintaining the small size of the breaker leaves littleroom to provide the additional force needed to compensate for thedifferences in manufacturing tolerances. The requirement for simpleconstruction and low manufacturing costs must also be considered.Further, the entire modular system should be symmetrical so thattripping may take place in a multiple arrangement without the necessityfor any breaker being left or right handed. In other words, identicalsurfaces must be presented to a symmetrical tripping member.

Additionally, there must be a complete absence of the couplingsinfluence in the relatching cycle of the breaker units. That is, upontripping, the better conventional circuit breakers not only part thecontacts, but further throw the handle to off to allow visualinspection; simultaneously all the internal components of the circuitbreaker' are reset so that upon a single throwing of the handle to on,the contacts are closed. The coupling member must not interfere withthis function within either the breaker which has been automaticallytripped, or in the breaker which is being depcndently tripped.

3,505,621 Patented Apr. 7, 1970 OBJECTS OF THE INVENTION Accordingly, itis the object of this invention to provide an interlocking triparrangement for two pole and multipole circuit breaker operation whichsatisfies the foregoing considerations.

It is a further object of this invention to provide such interlockingtrip arrangement with minimum modification to existent breakers.

BRIEF SUMMARY OF THE INVENTION The invention is predicated upon theeffect of a scissor camming action upon a rolling surface. The rollingsurface is provided by a cylindrical interlocking or coupling memberwhich is interposed between the breaker movable armature and the memberwhich it latches. A first camming surface is provided in the latchedmember and a second in the body of the breaker. These two surfacesprovide ascissor-type cam which acts upon the cylindrical couplingmember when either breaker trips, thereby effecting the tripping of theother breaker.

The above mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will best be understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, the description of which follows.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a circuit breaker cutaway to reveal the inventive portion thereof; the remaining significantelements are shown in phantom;

FIGS. 2a and 2b are :details of the inventive portions of the circuitbreaker in two positions of operation;

FIG. 3 is an exploded perspective of a pair of circuit breakers coupledfor two pole operation; and

FIG. 4 is a perspective illustration of the trip coupling memberaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the drawings, andin particular to FIG. 1, there may be seen a magnetic circuit breakersuch as is generally disclosed in U.S. Patent No. 3,305,806 issued Feb,21, 196-7 to the same assignee. While a detailed analysis of thisbreaker may -be had by reference to the foregoing patent, suicientparticulars shall be set forth below to allow an understanding of thepresent invention. It is to be understood, however, that the patentedbreaker is illustrated for purposes of example only and that anyconventional breaker may be employed in conjunction with the inventionso long as the requisite camming surfaces are available and functionrelative to the latching mechanism in the manner to be described.

Pivoted manually-operable handle 10 is housed within the breaker casing112, and is biased internally counterclockwise. Pivotally mounted uponan extension 10' of the handle is a toggle link 14. Toggle link 16 inturn is pivotally coupled to toggle link 14 within a channel 14' and isurged to the extremity of this channel by spring 15. The three membersthus far described cooperate to form a double toggle assembly having acentral energy-storing link (14). The only fixed/pivot in the toggleassembly is that mounting the handle to the circuit breaker housing atpoint a.

A more detailed analysis of this assembly and its functions duringcircuit breaker cycling can be had by reference to the above-denotedpatent. Suffice to say that the toggle assembly produces several netforces. The first of these forces is a downward force on movable contactmember 18 which carries contact 19. Since this force occurs to the leftof pivot c, it opposes the bias force provided by spring 22 andmaintains contact 19 in engagement with contact 21, carried bystationary contact member 23.

Line-to-load continuity is established through the flexible lead 2S,which is aflixed to a wire connector (not shown), movable contact member18, stationary contact member 23, electromagnet coil 27, and busbarcontact 29.

Thesecond force produced by the toggle assembly is imparted to the triplever 30 which is pivotally mounted at point b. This force is appliedcounterclockwise at contact point d and is produced as a consequence ofthe sum of the forces on toggle links 14 and 16. The net forces on thetoggle assembly further act to maintain the handle at its clockwiselimit; overcoming the internal counterclockwise moment of the handle.

Trip lever 30 is maintained in the position shown and is latched againstcounterclockwise rotation by lip 31 of movable armature 32.

Coil 27 generates a magnetomotive force dependent upon the currentpassing through the circuit breaker. The resultant fluX travels amagnetic path which includes air gap 34, core 36, side armature or theyoke 38 of movable armature 32 (pivotally mounted upon yoke 38). Exceptfor the air gap, the circuit is of low reluctance. The force upon theopposing surfaces at the air gap is a function of the coil current.

At overload, which is the existence of predetermined current for apredetermined time, the force is such that the gap is reduced to zero bymovement of one end of the movable armature 32 to the core 36. At theother end, the movable armature delatches trip lever 30 and the force atpoint d now rotates the lever counterclockwise. The rotation of thelever is followed by movement of toggle links 15 and 16 at theirjunction (hereinafter called knee) to the right. The movement of theknee to the right causes an intermediate portion of toggle link 16 tostrike an abutment in the molding at point e resulting in the bottom ofthis link moving to the left and sliding off contact member 18. Contacts19 and 21 thereupon snap open by virtue of the force imparted by spring22. There are now no forces acting upon the toggle assembly other thanthe internal bias acting upon handle and urging it counterclockwise.

The handle bias serves the reset function by rotating the Whole toggleassembly to the right. Rotation of the lower portion of the handle link,generally denoted at 3S, to the right causes it to engage trip lever 30at the juxtaposed arcuate section and return it to the right. Spring 39on the movable armature biases this armature to the latch position whenthe end of the trip lever clears li 31.

pThe circuit breaker has now been reset but is not on. Return of thecircuit breaker to the on condition is performed by rotating the handleback to the position shown in FIG. l. The foregoing is deemed sufficientfor an understanding of the invention and the modification necessary tointercouple the circuit breakers for multipole operation. A moredetailed analysis of the various functions may be had by reference tothe patent.

Turning now to FIGS. 2a and 2b, the inventive details will now bedescribed. In these figures, as well as in FIGS. 3 and 4, commonelements will bear similar reference numerals. As may be seen from thefigures, trip lever 30 includes a recess indicated generally at 40,having a camming surface 42. While this surface is shown as broken intotwo angled linear portions, it may also be a continuous curve. Theformer, however, is preferred since it places less load on the system.While not shown in the figures, trip lever 30 is symmetrical and amirror image recess appears on the back side of the lever arm for rightor left placement of each circuit breaker with respect to its polepartner. Riding in recess 40 between camming surface 42 and movablearmature 32 is trip coupling member 50, shown in section. A perspectiveview of this member may be seen in FIG. 4.

Dashed line 44 describes an aperture in the housing 12 for defining anddescribing the motion of the trip coupling member 50 upon movement ofthe trip lever 30 as follows.

Upon an overcurrent condition, air gap 36 is traversed by movablearmature 32 and trip lever 30, as described, is released and movescounterclockwise under force of the toggle assembly. As a consequence ofthis motion (see both FIGS. 2a and 2b) trip coupling 50 rides up cammingsurface 42 under the scissor action between this moving camming surfaceand the stationary surface portion 46 of aperture 44. Preferably portion46 is angled generally normal to the armature 32 for greatest lift.

FIG. 2b shows the nal position. Trip coupling member 50 is at the upperportion of the opening 44. At this juncture, it bears mentioning thattrip coupling member 50 will, by virtue of its cylindrical periphery,tend to rotate and minimize the friction upon the surfaces which itcontacts during its displacement.

The upward motion of the trip coupling member 50 will cause itsextension disposed similarly in a neighboring breaker to contact theunderside of movable armature 32 lifting it upwardly and unlatching thetrip lever of this breaker; allowing the toggle assembly to release thecontacts of the coupled breaker similarly to the action of the Masterbreaker. Upon reset, trip lever 30 moves to the right allowing tripcoupling member 5t) to drop back into the recess.

FIG. 3 is an exploded perspective showing the disposition of the tripcoupling member between adjacent breakers. In this figure, the breakeropening 44 may be plainly seen in the right breaker. A similar openingappears in the left brefaker. In order to prevent skewing of the tripcoupling member, a disc-shaped central portion 50 (see FIG. 4) isincluded. This portion rides in housing recesses 52 and 53, which servethe function of guiding the central disc S0 of the trip coupling memberand permitting the disc to electrically seal the breaker units from oneanother. That is, disc 50 serves as an insulating spacer regardless ofits position. Breaker holes 60 through 65- in the respective breakercasings permit the passage of rivets or bolting members (not shown) topermanently join the breakers for related operation.

A handle coupler 70 is provided to tie the respective breaker handlestogether. This is neecssary for manual operation. When handles are putON or OFF, both breaker mechanisms must operate in synchronization socontacts make or break simultaneously. A condition of one pole ON andthe other OFF should not exist.

Trip member Sil may be a machine turned or molded member made ofinsulating material with high dielectric strength (since as mentioned,it electrically spaces the live parts of joined poles). Only minimalmechanical strength is necessary because the forces involved are small.Exemplary materials for such a coupling member are gray fiber or moldednylon.

The foregoing description is applicable to not only two polecooperation, but any gang or multipole operation where the couplingmember of FIG. 4 is iteratively applied between adjacent breakers. Thisresult is attained as a consequence of all members related to theintercoupling function being symmetrical. Trip lever 30 has identicalcamming surfaces; trip coupling member 50 is symmetrical; recesses I52and 53 appear on both sides of the breaker and are symmetrical, and soon.

While the principles of the invention have been described in connectionwith specific apparatus, it is to be clearly understood that thisdescription is made only by way of example and not as a limitation tothe scope of the invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is:

1. In an electric circuit protection arrangement of the type includingindividually encased breakers, each having a pivoted manually operablehandle, a pair of complementary contact members maintained in contact, atrip lever biased in a direction for releasing said contacts; anarmature responsive to current through the breaker and normally latchingsaid trip lever in a position removed from the contact releasingposition, the improvement for combining a pair of juxtaposed breakersfor two pole operation comprising on each breaker similar cammingsurfaces on a trip lever portion adjacent a portion of said armature,said camming surface being at an angle of less than 90 with respect tothe direction of motion of said trip lever when moving to the contactreleasing position; a trip coupling member extending between adjacentbreakers and having cylindrical portions respectively interposed betweeneach camming surface and trip lever portion of each breaker; and acommon stationary camming surface intermediate said breaker trip levers,said carnming surface in combination with each of said trip levercamming surfaces producing a linear thrust on said trip membersubstantially perpendicular to the direction of motion of said triplever upon the overcurrent actuation of either armature for lifting theother armature.

2. The circuit breaker arrangement claimed in claim 1 wherein thestationary camming surface comprises an oblong opening in at least onebreaker casing Wall.

3. The circuit breaker arrangement claimed in claim 1 wherein said tripmember comprises a cylindrical member having a anged disc portionbetween its ends, said flanged portion riding a recess between coupledbreakers for preventing axial twist of said trip member and forsimultaneous sealing the opening between breakers.

References Cited UNITED STATES PATENTS 2,977,444 3/ 1961 Middendorf20G-116.13 3,116,387 12/1963 Middendorf 20G-116.13 3,193,646 7/1965Krebs 335-160 GEORGE HARRIS, Primary Examiner HAROLD BROOME, AssistantExaminer U.S. C1. X.R. 335-160

